FDA Approves Vitrakvi for Solid Tumors with NTRK Gene Fusions

The Food and Drug Administration (FDA) has granted accelerated approval to larotrectinib (Vitrakvi, Loxo Oncology and Bayer) for adult and pediatric patients with solid tumors that have a neurotrophic receptor tyrosine kinase (NTRK) gene fusion without a known acquired resistance mutation, that are either metastatic or where surgical resection is likely to result in severe morbidity, and who have no satisfactory alternative treatments or whose cancer has progressed following treatment.

This is the second tissue-agnostic FDA approval for the treatment of cancer.

Approval was based on data from three multicenter, open-label, single-arm clinical trials: LOXO-TRK-14001 (NCT02122913), SCOUT (NCT02637687), and NAVIGATE (NCT02576431). Identification of positive NTRK gene fusion status was prospectively determined in local laboratories using next generation sequencing (NGS) or fluorescence in situ hybridization (FISH). NTRK gene fusions were inferred in three pediatric patients with infantile fibrosarcoma who had a documented ETV6 translocation by FISH. The major efficacy outcome measures were overall response rate (ORR) and response duration, as determined by a blinded independent review committee according to RECIST 1.1.

Efficacy was evaluated in the first 55 patients with unresectable or metastatic solid tumors harboring an NTRK gene fusion enrolled across the three trials.  All patients were required to have progressed following systemic therapy for their disease, if available, or would have required surgery with significant morbidity for locally advanced disease. Twelve patients were less than 18 years of age. A total of 12 cancer types were represented, with the most common being salivary gland tumors (22%), soft tissue sarcoma (20%), infantile fibrosarcoma (13%), and thyroid cancer (9%).

ORR was 75% (95% CI: 61%, 85%), including 22% complete responses and 53% partial responses. At the time of database lock, median duration of response had not been reached. Response duration was 6 months or longer for 73%, 9 months or longer for 63%, and 12 months or longer for 39% of patients.

The safety of larotrectinib was evaluated in 176 patients enrolled across the three clinical trials, including 44 pediatric patients. The most common adverse reactions (≥20%) with larotrectinib were fatigue, nausea, dizziness, vomiting, increased AST, cough, increased ALT, constipation, and diarrhea.

The recommended larotrectinib doses are 100 mg orally twice daily for adults and 100 mg/m2 orally twice daily (maximum of 100 mg per dose) for pediatric patients.

FDA granted this application priority review, breakthrough therapy designation and orphan product designation.

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